Particulate burners, such as "pellet" stoves, typically burn the particulate material in relatively small quantities. The pellet material is usually fed from a hopper containing a large quantity of pellets. Some form of metering device is provided between the hopper and burner in order to control feed of pellets to the burner. The feed mechanism is typically controlled in speed or for timed intervals in order to control the amount of pellets fed. Such varied feed will affect heat output for the associated burner. Several problems have been recognized with such known forms of feed systems.
Many conventional pellet feed systems employ an auger for feeding the particulate fuel laterally from a hopper. These systems have long been known to jam or bind against the fuel particulates, especially if the particulate material is not uniform in size and quality. "Jamming" can cause damage to the feeding system, or cause frustrating down time for the pellet burner while the auger path is cleared. "Burn back" into the auger area has also been experienced.
Jamming is also a problem with other forms of metering wheels and other arrangements where it is possible for a piece of particulate material to be wedged between the metering device and a wall of the housing enclosing the metering arrangement.
Another problem with prior forms of particulate metering systems is that they cannot be relied upon to deliver fines along with the fuel. This is especially true where precautions are taken to avoid the jamming problem discussed above. If tolerances are left slack to avoid jamming, the fines tend to collect in the designed voids and are not delivered to the combustion area.
A still further problem is encountered in break up of the particulate material as it is delivered. This is especially true of high torque auger systems that avoid the jamming situation by forcibly rotating the auger or other feed mechanism to deliver the material. Jamming is eliminated by crushing any particulate material that would otherwise jam the system. This creates more fines and increases another problem that is common to many forms of feed mechanism-noise.
A still further problem realized in many forms of particulate feed mechanisms is the amount of time between hopper loading and the actual time fuel is delivered to the combustion area when the feed mechanism starts from an empty condition. This is particularly true of auger feeders where the slowly moving augers take substantial time to deliver fuel from a newly loaded hopper. This can be inconvenient and frustrating, especially in cold conditions where the burner has run out of fuel and the fire must be restarted.
The present invention, as will be understood below, eliminates the above problems by providing a feed system in which particulate fuel is delivered from a hopper to a burn pot in an accurate, reliable, quickly-responsive, quiet, and jam-free manner.